I think it was partly the recipe that I had which didn't call for sugar and the fact that I probably cooked the onions too quickly and the fond got bitter. Thanks to all! I can't wait to try your recipes!

Glorie, the recipe I use is similar to what Jeekinz posted (not sure why you titled the link "A caveman could do it" ... ?)

I think that is a reference to the Geico commercials about it being so easy a caveman could do it! I've never made FOS but from reading this thread I'm going to have to try it. I LOVE FOS and DH LOVES anything onions so we may just have a winner if I can successfully make my own!

Canned beef broth tends to be bitter, so I use half beef and half chicken. I also make it when Vidalia onions are in season.
Patience is required to caramelize the onions. Do it low and slow. If you cook the onions in a non-stick pan, you only need a couple tbls of EVOO and a couple of butter. If you are using onions that are not as sweet, add a pinch of sugar to the pan.

If your finished product tastes a little bland, add a packet of dry French onion soup mix. No one will know unless you tell the.

I only use chicken stock for mine, & I'm so used to it now that I find beef stock versions too strong for me. I find a good chicken stock - either homemade or your favorite commercial brand - melds very nicely with the caramelized onions & doesn't overpower the wine & cognac.

I always use a mix of beef and chicken broth. Seems to give a better flavor.

Ditto on the mix of broths - it REALLY smooths out the flavor. I also use red onions, white onions, and leeks in mine. A dash of Port and a dash of Burgundy. I take my time with the onions; getting them to the right color. No need to hurry.